Method of making preloaded bearings



Aug. 21, 1956 C. B. SMITH 2,1 2

METHOD OF MAKING PRELOADED BEARINGS Filed NOV. 18, 1952 FIGJ 2 Sheets-Sheet 1 FIG. 2

ATTORNE Aug. 2 1, 1956 c. B. SMITH 2,759,243

METHOD OF MAKING PRELOADED BEARINGS Filed NOV. 18, 1952 2 Sheets-Sheet 2 FIG. 4

FIG. 5

INVENTO 61092715 5172 United States Patent METHOD oF MAKING PRELOADED BEARINGS Clifford B. Smith, Birmingham, Mich., assignor to Vinco Corporation, Detroit, Mich., a corporation of Michigan Application November 18, 1952, Serial No. 321,105

2 Claims. (Cl. 29-1484) hearing must be avoided so that the rotating part will remain accurately centered at all times. An ordinary ball bearing, that is, one which is not preloaded, will under load develop some lost motion, depending on the relation of the load to the size of the bearing and the compressibility of the metal. Since there is very little variation in the compressibility of the different steels used in the manufacture of bearings the lost motion resulting from loading of the bearing may be said to be dependent on the ratio of the load to the size of the bearing. By preloading the bearing the lost motion resulting from a given size is'materially reduced. That is to say, there will be no lost motion until the load on the bearing exceeds the preload placed on the metal of the hearing when the bearing is assembled. Hence, for a given load and a given lost motion tolerance, a smaller preloaded bearing can be used than one that is not preloaded.

By my improved process preloaded bearings of any desired degree of preload may be made from the same parts as standard bearings which are not preloaded and at a cost but little more than that of ordinary bearings.

My improved process is applicable to bearings of all types and in the accompanying drawings I have illustrated several types of bearings which may be made by my improved method.

In Figs. 1 and 2 I have illustrated a single-row, radial bearing wherein the ball races are formed of single rings with corresponding ball grooves.

In Fig. 3 I have shown a type of bearing wherein each ball race is formed of two separate rings with matching grooves.

In Figs. 4, S and 6 I have illustrated a common form of 45 bearing wherein the races are formed, respectively, on the spindle and on the hub of the rotating part.

The bearing illustrated in Figs. 1 and 2 consists of a spindle 1 having a reduced end portion 2 for receiving the inner ball race 3 with a threaded extension for the clamp nut 4. The outer ball race 5 is seated in an annular groove 6 at the outer end of the hub 7 of the rotating member and is held in place by a cap 8 fastened to the hub by screws 9 in the usual manner. The parts shown and described constitute a common type of bearing which is widely used in a great variety of machines.

In assembling a bearing of this type the balls 10 are added to the bearing after the above described parts are assembled. This is accomplished by the provision of a plug 11 which is seated in a hole 12 in the hub and over- 2,759,243 Patented Aug. 21, 1956 lying a hole of smaller diameter in the outer ball race. The plug 11 has an outer part of a diameter to fit the hole in the hub and an extension of smaller diameter to fit the hole in the ball race. The inner end of the plug is shaped to conform with the shape of the ball race and is preferably hardened and ground so as to form a smooth continuation of the ball race. The plug is held in place by a tapered screw 13 as shown in Fig. 1.

To preload this bearing several sizes of presorted bearing balls varying in size by minute dimensions, say, for example, five ten-thousandths of an inch, are supplied. Bearing balls are normally so graded by the manufacturer and are accurate to plus or minus one ten-thousandth of an inch.

After the parts are assembled, except the balls, the operator fills the ball race with balls of the largest size that will permit the plug 11 to be pushed into place without the application of significant force. When loaded with balls of this size, the bearing contains the largest balls which can be used in a free-running non-preloaded bearing. After determining the size of the balls to produce a nonpreloaded bearing, the operator removes these balls and substitutes balls of larger diameter, either five ten-thousandths or ten ten-thousandths larger, depending upon the degree of preload to be supplied to the bearing. In assembling these larger balls of the bearing the plug 11 is pushed down against the last ball, which requires the application of some little force. The plug is then fastened in place by screwing in the screw 13 to thereby seat the head of the plug firmly against the outer wall of the ball race. The

- bearing will be now accurately preloaded to the extent de- I, manner .abovedescribed, that is, by substituting larger balls after thebearing is assembled with the balls of proper size to allow no lost motion when the bearing is running without load. This bearing, however, may be preloaded by altering the size of the race instead of the size of the balls. In the bearing of Fig. 3 the inner ball race is formed of two parts 13a and 13b which are separated along their median transverse plane. Similarly, the outer race is formed of two parts 14a and 14b.

In assembling this bearing the balls are assembled between the two halves of the two races and the assembled bearing then placed between the spindle 1 and hub 7, and clamped in place by the clamping nut 4 and cap 8. The bearing is first assembled with balls of a size such that the two halves of the two races can be pressed into contact without the application of significant force. The halls can then be removed and larger balls substituted, as above described, or the meeting faces of the two halves of the two races may be ground ofif a few ten-thousandths of an inch, depending upon the degree of preload which it is desired to give to the bearing. The bearing is then reassembled and the two halves of the two races clamped together by means of the clamping nut and cap.

A hearing such as illustrated in Figs. 4, 5 and 6 where the races are formed directly on the relatively rotating parts may be preloaded in the same manner as the bearing shown in Figs. 1 and 2. The bearing here shown comprises a spindle 20 having spaced ball races 21 near each end of the spindle, the races being each at an angle of 45 to the axis of rotation so that the bearing serves both as a radial bearing and a double thrust bearing. The rotating member comprises a gear with an integral hub 22 formed with races 24 complementary to those on the spindle.

In assembling this bearing the balls 23 at the outer end of the bearing are assembled between the two races, with the axes of spindle 2t] and hub 22 vertical, the outer end of spindle 20 is uppermost and raised within hub 22 to provide a suificient annular gap for the introduction of the balls. Hub 22 and spindle 20 are then shifted to the relative position shown in Fig. 4 to hold this row of balls iii place; The Balls o f tlie ether eating are tiiti dropped through an opening 25 in the hub; which opening is cldsd by a ping" 2 'lar to the time 11 above described, and held iii place by a sjetew 27, 7

The b'alls thus selectedas atiove described are of the proper size to provide he lost motion when freely rotating tinder iio -lo'ad conditions. The balls at the inner end (if the bearing are then removed aiidballs er five or ten tenthoilsa'r'idths greater diaiiie r stitis'titut'ed, the last ball being pressed into place by" force exerted through the plug 26-. This forcing ofthe last ball in piee preieads both sets of teenage as the pressure of the balls against the race as the test ball is forced into place tends to shift the gear to the left against the other set of balls so that the resulting e6" pression in the teeter is distributed equally between both bearings;

By improved process the cost of preloading bearing's is reduced to an insignificant addition over the cost of fidii pre loaded beatings. No greater precision is required iii the manufacture of the parts, the accurate preloading being obtained not by precise manufacture of the races, But 6v e e aiid try selection 6f the balls which are atways of precise dimension because they are sorted after inane-tenure by mechanical sorting devices which operate with great p'rci's'ioii.

In the fore ding specification and drawing I have deserihed and shown several different types or bearin s and now my improved method er manufacture can be applied thereto; It will be understood, however, that the invention is not limited to' the bearings illustrated, but (in the contrary, the satire principle may be applied to various other forms at Bearings, and the appended claims are not to be construed to be limited to any particular type of bearings except as insofar as recited in the claims;

I claim:

1 The method of making preloaded bearings which comprises pi'ovi ding opposed ball races one of when has a fitting o enin and a removable closing p'lu inserting bearing balls into the race through said opening of such size that the final ball projects partially into said opening, and then forcing said plug into said opening to an extent to maintain said ball in annular alignment with the other balls of said bearing, and locking said plug in such positlon.

2. The method of making double row preloaded bearings' which comprises providing two axially spaced ball races which are opposed in the axial direction at least in pm, each of said races comprising a pair of race membets, and one member er one pair of which has a filling opening and a removable closing plug, supporting the bearing with its axis extending in an upward direction and with the ball race at the top which does not have a filling opening, axially separating said race members and filling said upper ball race by inserting bearing balls therein and reclosing said race members, then inserting into the unfilled ball rac through said filling opening bearing balls er siicii size that the neat ban piojects partially into said opening, and then forcing said plug into said opening to an extent to maintain: said ball in annular alignment with the other balls of said race thereby simultaneously preleading the bails of both of said races, and locking said plug in such position.

References 'Cited in the file of this patent UNiTED STATES PATENTS 327,408 Pihlfeldt Sept. 29, 1885 777,698 Sharp Dec. 20, 1904 1,622,678 Ellwein Mar. 29, 1927 1,722,492 Br'u'nner July 30, 1929 2,037,982 Hughes Apr. 21, 1936 2,259,324 Robinson Oct. 24, 1941 2,606,361 Keller z Aug. 12, 1952 REFERENCES H Roller Bearings (R. Allan), published by Pitman Publishing Corp., second edition, 1946. Page 237, lines 11 to 13 relied oil. 

